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Origin 50 valve bias?

Discussion in 'The Workbench' started by GibboPete, Sep 21, 2021.

  1. GibboPete

    GibboPete New Member

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    I'm looking to change the valves on my Origin 50, 2 years old, loads of use. May have been dealt with before but can anyone advise on biasing the output valves please. I was planning to get a matched pair of EH's, will they need biasing? I have a mate who can do it if so, but he's struggling to find a schematic of the 50. Love the amp, run into a Blackstar Cab with Vintage 30's in. Thanks in advance.
     
  2. fitz288

    fitz288 Well-Known Yinzer Silver Supporting Member

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  3. MarshallDog

    MarshallDog Well-Known Member

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    Yes it will need biasing and its simple. All he needs is a bias meter a digital volt meter.
     
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  4. pedecamp

    pedecamp Well-Known Member

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    Watch this : https://www.eurotubes.com/store/pc/generic bias video.htm

    Welcome to the forum! :yesway:
     
  5. fitz288

    fitz288 Well-Known Yinzer Silver Supporting Member

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  6. GibboPete

    GibboPete New Member

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    Many thanks for the welcome and the info - above my paygrade but I've forwarded the links to a good techie friend of mine who undertsands this stuff.
     
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  7. syscokid

    syscokid Member

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    Surfing through, and I spotted this thread with interest...

    If the new power tubes are guaranteed to be matched, then all you need is a meter. With one of the meter's probe to any ground on the chassis, find C32 and probe the square pad. The circular pad is also a ground. Marshall recommends 70mv (35mv per tube). 70mv's @ 430v at the EL34 power tube plates is considered a "medium" or 60% bias.
    20210905_130113.jpg
     
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